Siightt: Wow, nice, I picked these up not too long ago, but had no idea a new game was coming out. I loved them back in my childhood, and decided I'd love to play them over...and now finding out a new one is coming...very awesome.
My suggested order is MM and on, skip first...go back to it if you have time. I believe Martian Memorandum was a typical type adventure game, whereas the first one had a flight sim if I remember correctly...been so long...but I can't remember If i even bothered finishing it.
Good luck,
plumgas: most people will tell you to skip these first 2 as they are not in the same class as the later games. Personally I would start at UAKM .
Those people aren't true Tex Murphy fans*, because Tex's first two adventures are as great as the rest. I especially like Mean Streets, which is IMO better than Martian Memorandum. I strongly recommend playing Mean Streets before Overseer, because while the basic storyline is same the narrative and gaming experience is very different.
*I apologize if this statement insults someone, but you don't see this kind of behavior among other fan communities. For example King's Quest fans don't tell you that you should skip the early AGI games and focus just to later games of the series. Active attempts to discourage others from exploring where the legend of Tex Murphy started and preventing them from enjoying his earliest adventures aren't just fan behavior.